Law & Disorder —

Houseguest downloads child porn, cops show up

Giving out your Wi-Fi password always carries at least some risk.

Do you really know how your various friends, relations, acquaintances, and hangers-on plan to use your Internet connection when they drop by and ask for "the Wi-Fi password"? Unlikely—and yet anything that they do illegally through your home network can bring cops to your door with search warrants, asking tough questions about child pornography.

Case in point: Marin County, California, just north of San Francisco's Golden Gate Bridge. Local police in Marin communities like Novato are members of the regional Internet Crimes Against Children (ICAC) task force, and as such they participate in the common law enforcement practice of monitoring peer-to-peer file-sharing networks for possible child pornography files. In September 2013, Novato detective Amy Yardley was looking for such files being traded from Marin County IP addresses, and she scored a hit on the Ares network with a suspicious file downloaded by a Sausalito Internet subscriber.

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Yardley passed the tip to the Sausalito Police Department, where detective Brian Mather obtained a search warrant for the subscriber's address. He showed up at the house with a search team but couldn't find any child pornography within. The home's residents, no doubt unnerved by both the search and the charge behind it, pleaded their innocence and gave Mather a complete list of all houseguests who had used their wireless network in recent months.

Investigating this list took months, but Mather eventually developed a suspect: Mark Magner, age 32, from nearby San Rafael. Police then searched Magner's home and seized his computer. A forensic examination of the machine turned up "multiple videos and pictures that depicted juveniles and children involved in sexual acts," in the words of a police department press release.

Mather called Magner in to the Sausalito police headquarters on April 22, told Magner what had been found on his computer, and arrested him. On May 9, the Marin County District Attorney filed charges in state court, accusing Magner of one count of "possession or control of child pornography." Magner is scheduled to enter a plea at a hearing next week.

Password, please

Offering the use of your property or services to houseguests has always carried some small risk of summoning police—uncle Leo might borrow your car to go buy some smokes but sideswipe someone along the way, while cousin Carrie might be going through a rough patch during which she finds it amusing to call in bomb threats to the local delicatessen. Still, the sheer ubiquity of Internet-enabled devices means that nearly every houseguest who spends more than a few hours with you will likely have access, under your IP address, to a network which they can use to defame, harass, victimize, spam, defraud, hack, or download. (Even my parents—no technological gadget hounds—have one iPad each... and take them everywhere. Fortunately, they're unlikely to attract the watchful eyeball of the state.)

A vocal segment of Internet users has suggested for years that one can simply claim the "someone else used my Wi-Fi" defense (sometimes as a way to cast doubt on just who in the home might be downloading films online). And it's true—the defense is real and it can work. But it's the sort of plea you only get to make after a warrant service team of armed police have turned your home inside out and have you seated on the living room couch as they stare you down and ponder a detailed forensic search of every gadget in your home.

In other words, it's not the sort of argument one wants to be in the position to make. But what else to do? Be a bad host by getting parsimonious with the network password? Ask your guests to sign some kind of "Terms of Service" document first? A Wi-Fi password is the new "can I get you a cup of water?", and though there are ways to set up secondary guest networks and take other security and control measures, it's difficult to mitigate these risks completely—and most Internet users wouldn't know what steps to take, anyhow.